A bite block is a device commonly used during upper gastro-intestinal endoscopic procedures to facilitate passage of an esophago-gastro-duodenoscopy (EGD) endoscope. The purpose of the bite block is to allow the physician to perform the procedure without the subject interfering by biting and damaging the endoscope tubing inserted via his mouth, whether voluntarily or involuntarily.
The upper gastro-intestinal endoscopic procedure itself, together with the use of a bite block, is often highly uncomfortable for the subject. For this reason it is very common for the subject to be sedated during the procedure. The sedative helps the subject to tolerate the procedure, rather than to oppose it, thus enabling the doctor to perform the procedure undisturbed.
Despite this, it is common for the subject to show opposition to the procedure. The subject will often resist entry of the endoscope by not swallowing as requested and by tensing his or her muscles. The subject will also often oppose the placement of the bite block itself before the procedure, and more commonly during the procedure because of involuntary muscular reactions, by trying to manipulate it out of his or her mouth by means of the tongue or teeth.
Prior art bite blocks are generally characterized by a number of structural features:                1. A tubular body or barrel whose internal lumen serves as the channel for passage of the endoscope, and whose top and bottom outer surfaces serve as the surfaces upon which the subject's teeth bite. These surfaces are generally flattened.        2. A wall centrally connected to the outer end of the tubular body, shaped such that it should lie comfortably outside and around the subject's mouth. It is this wall that fulfils the double function of providing a general alignment direction to the tubular body and of preventing the bite block from falling into the mouth. The wall is also known as the front plate.        3. A band connected to the bite block and used to strap the bite block firmly to the subject.        
A number of bite blocks are described in the prior art, which add additional features to the above-mentioned basic features. The additional features are generally directed to assisting the physician in performing the endoscopic procedure with minimum interference from the subject, by making it more difficult for the subject to oppose the bite block, which generally means making it more difficult for the subject to eject the bite block from the mouth. Thus in U.S. Pat. No. 5,174,284 to F. W. Jackson for “Endoscopic bite block”, there is described a bite block with, inter alia, (i) a tubular outer surface whose upper and lower walls are sloped towards each other in the direction of the front plate, so that as the subject's teeth bite down on the surfaces, the bite block tends to move back into the mouth where it seats more firmly; and (ii) a tongue depressor, which firmly forces the tongue downwards as the teeth compress against the upper and lower surfaces of the bite block channel, keeping the tongue seated below the mouthguard, where it cannot struggle to push the block out of the mouth. Additionally, the bite block has rear teeth guards, which require the mouth to open very wide in order for the bite block to fall out. In U.S. Pat. No. 6,257,238 to N. M. Meah, for “Bite block for upper gastrointestinal endoscopy with tongue depressor”, there is described another bite block with a tongue depressor, though the tongue depressor is therein described as preventing the tongue from covering the channel of the bite block, and blocking the subject's throat.
One of the physiological effects of the use of such bite blocks is that a sensation of oral immobility may be generated because of the way in which such bite blocks operate. The bite block may thus be uncomfortable for the subject and may produce a feeling of being gagged even before the insertion of the endoscope itself. Furthermore, large amounts of saliva are commonly produced during these procedures, and since one method of dealing with saliva is by manipulating it with the tongue, depressing the movement of the tongue may prevent the subject from dealing with it, again causing the subject to have a choking feeling. This general physiological feeling may increase the subject opposition to the procedure even more, thus negating the initial, intended purpose of the invention.
In addition to the problems associated with the comfort and ease of use of prior art endoscopic bite blocks, a further problem exists when such prior art bite blocks are used together with breath sampling means, in particular capnographic sampling, or gas delivery, such as oxygen. It is common in endoscopic procedures for the doctor to try to reduce the opposition of the subject to the procedure by administering sedatives. However, as with all sedation procedures, careful monitoring of the subject must then be performed, usually on a continuous or semi-continuous basis, to avoid the adverse affects of over-sedation.
It is well known that a sedated subject is vulnerable to episodes of hypo-ventilation and apnea. The ability to adequately monitor and detect these episodes is essential when potent sedatives are employed. Pulse oximetry, to determine the blood SpO2 level, is routinely used during these procedures, and provides a sensitive and reliable estimate of arterial blood oxygenation. While breathing room air, apnea causes arterial oxygen de-saturation and can thus be speedily detected by means of pulse oximetry. However, when subjects receive supplemental oxygen, as is recommended during sedation where breathing may be suppressed, apnea-induced oxygen de-saturation would be delayed until hyper-capnia ensued. For this reason, capnography, the continuous measurement of carbon dioxide in the breath, is generally recommended as a more appropriate and direct means to monitor for hypo-ventilation and apnea.
During medical procedures other than upper gastro-intestinal endoscopy the sedated subject is easily monitored with a capnograph, which continuously samples the subjects' breath. This is realized using an appropriate breath sampling cannula device connecting between the subject and the capnograph. The cannula is appropriately positioned in close proximity to the subject's nose, or nose and mouth. The capnograph, using a pump, continuously extracts breath from the subject via the cannula, to the capnograph sensor for analysis. One example of such a sampling cannula device is described in U.S. Pat. No. 6,422,240 to G. Levitsky et al, for “Oral/Nasal Cannula”, assigned to the assignee of the present application, and herewith incorporated by reference in its entirety.
In the prior art, CO2 sampling during upper gastrointestinal endoscopy, and especially during long duration procedures performed under sedation, monitoring is often performed using a separate nasal or oral/nasal cannula in conjunction with the bite block. Concomitant use of prior art bite blocks and cannulae is often not an optimal solution, and the capnographic performance may be noticeably affected. The generally applied method of using a prior art adjunct oral/nasal cannula with a prior art bite block, is to put on the oral/nasal cannula after the bite block has been inserted, such that the oral prong sits outside of the front plate of the bite block and is often mis-positioned or occluded by the bite block, or is located directly in the path of the endoscope and consequently pushed aside or even bent back when the endoscope is inserted. There is essentially “competition” for the use of the subject's oral passage between the need for oral breath sampling and the need for the passage of the endoscope, and since the endoscope procedure is the mission being undertaken, it generally prevails over the needs of the capnographic sampling.
The alternative use of a nasal sampling cannula, in an attempt to overcome this problem, is generally inadequate, since it is known that during upper gastro-intestinal endoscopic procedures, it is usual for the subject to perform largely oral breathing alone, and the effectiveness of the nasal sampling is much reduced. However, if oral/nasal sampling is performed in an attempt to overcome this problem, even if the oral sampling opening is placed in such a position so as not to interfere with the region required for the insertion and maneuvering of the Endoscope, the existence of majority oral exhalation still leads to another problem when using prior art devices. When the subject's mouth is wide open, as it is during upper G-I endoscopy, the excess breath pressure within the oral cavity is very small, and the exhaled breath therefore becomes diluted with the inhaled air, and sampling is thus inaccurate.
For the delivery of supplementary oxygen during endoscopic procedures, there exist in the prior art, a number of combination bite block/oxygen delivery cannula devices, such as those described in U.S. Pat. No. 5,273,032 to T. J. Borody, for “Oxygenating oral medical appliance” and in U.S. Pat. No. 5,513,634, to F. W. Jackson, for “Combination integral bite block airway and nasal cannula”, both herewith incorporated by reference, each in its entirety.
Both of these patents describe methods for delivering supplemental oxygen during upper gastro-intestinal endoscopy from a single, integrated device. Unlike the situation with carbon dioxide sampling, the use of a single device that integrates the bite block with oxygen delivery is mainly important for convenience, and is not mandated for providing optimal performance. A standard, separate oxygen supply nasal cannula could readily be positioned so as to adequately provide oxygen to the subject even when a separate bite block is in place. This is not the case when a separate breath sampling cannula is used simultaneously with a separate prior art bite block, as explained above.
One possible disadvantage of the integrated device described in U.S. Pat. No. 5,273,032 is that the oxygen is delivered via two tunnels with ends that do not reach the nasal cavities, but instead direct the oxygen gas stream towards the nasal cavities. The ability of these devices to efficiently direct the oxygen gas stream to the nasal cavities is thus dependant on how well the bite block sits in its intended position within the subject's mouth. Any tilt of the bite block inevitably causes a tilt in the direction of the nasal tunnels and consequently misdirects the oxygen gas stream away from the subject's nostrils. Such tilting of prior art bite blocks, or of the combination bite block/cannula device of U.S. Pat. No. 5,273,032 is common, as described hereinabove, either because of a feeling of discomfort when the bite block is in the mouth, causing the subject to attempt to move it, or because of the tilt generated by the placement position of the teeth in such prior art bite blocks, as explained above. The integrated device described in U.S. Pat. No. 5,513,634, on the other hand, is equipped with nasal prongs of a soft material, that do reach the nostrils of the subject. However, even with this device, tilting of the bite block causes the prongs to be tilted also, and may consequently cause them to exit the nostrils. The correct seating of the bite block is therefore likely to have an effect also on the efficacy of oxygen delivery also.
There therefore exists a need for an endoscopic bite block which fits comfortably into the mouth of the subject, without imposing any unnatural constraints on the subject's oral position, and consequently which reduces sensations in the subject that would cause the subject to oppose its presence. Furthermore, there exists a need for such an endoscopic bite block which enables accurate breath sampling, even in conditions of open mouth oral breathing, and which does not interfere with the endoscopic procedure.
The disclosures of each of the publications mentioned in this section and in other sections of the specification, are hereby incorporated by reference, each in its entirety.